1. Field of the Invention
The present invention relates to an endoscope apparatus and a method for detecting deterioration of a polarizer of an endoscope.
2. Description of the Related Art
Conventionally, endoscopes have been widely used in medical and industrial fields. For example, in the medical field, a surgeon can conduct examination of the inside of a subject by inserting an insertion portion of an endoscope into the subject and displaying an image of the inside of the subject picked up by an image pickup section provided at a distal end portion of the insertion portion on a monitor.
The distal end portion of the insertion portion of the endoscope is provided with an illumination window and an observation window. An illumination light is emitted from the illumination window to illuminate the subject, and a light reflected from the subject is received by an image pickup device through the observation window.
A polarizer is provided for each of an illumination optical system provided for the illumination window of the endoscope and an observation optical system provided for the observation window. For example, by causing polarization directions of the two polarizers to be the same, only a light from a mucosal surface of the subject is received by the image pickup device so that a surface structure of a mucosa can be easily seen. It is also possible to prevent halation by causing the polarization directions of the two polarizers to cross at right angles, as disclosed in Japanese Patent No. 2588460 and Japanese Patent Application Laid-Open Publication No. 2007-143580.